1. Field of the Invention
This invention relates generally to a winding and re-winding apparatus driven by a D.C. motor with an electronic commutation device. Specifically the invention pertains to control of a D.C. motor based on the polarity and absolute magnitude of a signal proportional to the deflection of a position sensing member.
2. Description of the Prior Art
Winding and re-winding devices are generally known. In such winding and re-winding apparatus a D.C. motor driving a winding or unwinding spool is controlled for the purpose of keeping constant the tension of the material being wound or unwound. Such a control must not only accelerate but also decelerate the spool if required. Therefore, the D.C. motor must be appropriately controlled by a position control. In the prior art, D.C. commutation machines have been used to drive the spool in the winding or re-winding apparatus. Control of the acceleration as well as the deceleration of the motors is possible only through the use of a closed-loop control system. This control system is switched appropriately as a function of the polarity of the position control output signal.
Due to the fact that commutation motors need constant servicing, it is advantageous to employ in their place maintenance-free brushless D.C. motors. However, a brushless D.C. motor cannot be reversed by simply reversing the polarity of the input voltage which makes impossible the simple replacement of a commutation motor by a brushless D.C. motor.
It is an object of this invention to create a winding and re-winding apparatus which is equipped with a brushless D.C. motor the speed of which can be accelerated as well as decelerated by a control loop driven by a position sensor.